Method of forming heat exchange tubes

ABSTRACT

A method of forming a heat exchange tube having an extended surface configuration impressed on the lateral sides thereof. A longitudinal embossing is formed on the surface of a plane sheet and the extended surface is impressed thereon prior to its being formed in a suitable die arrangement that locates a bend at a predetermined location marked by the longitudinal embossing.

United States Patent Inventors George K. Goetschius METHOD OF FORMING HEAT EXCHANGE TUBES 10 Claims, 6 Drawing Figs.

US. Cl .L 113/118, 29/1573.29/477:72/368.72/398: 113/120 Int, Cl B21d 53/02 Field ofSearch 72/398;

72/368; 113/118, 116U; ll3/120W;29/l57.3,477

References Cited UNITED STATES PATENTS 8/1924 Treanor 1 13/120 5/1933 Kloss et a] 72/398X 3/1935 Light 113/118X 8/1964 Eichner et al 6/1968 Phillips 1 13/1 20X Primary Examiner-John F. Campbell Assistant Examiner-D. C. Reiley Attorney-Wayne H. Lang and Eldon H. Luther ABSTRACT: A method of forming a heat exchange tube hav- .ing an extended surface configuration impressed on the lateral sides thereof. A longitudinal embossing is formed on the surface of a plane sheet and the extended surface is impressed thereon prior to its being formed in a suitable die arrangement that locates a bend at a predetermined location marked by the longitudinal embossing.

1 METHOD OF FORMING HEAT EXCHANGE TUBES BACKGROUND OF THE INVENTION This invention relates to' an improved method of forming a tubular heat exchange member and is-a substitute for application Ser. No. 593,937 filed on Nov. 14, 1966, now abandoned, entitled Heat Exchanger Tubes.

The present invention relates to a tube-type heat exchange apparatus such as commonly utilized for the transmission of heat between plurality of fluids. More particularly, this invention relates to a tubular element for such heat exchange apparatus and to a unique method of producing the tubes confining the flow of fluids therethrough.

To enhance the flow of heat between inner and outer walls of a heat exchange tube it has been a'common practice in the past to place an extended surface on the inner or outer walls. Such extended surface has commonly taken the form of fins or other protrusions on thewalls of thetubes that extend outward therefrom and into the stream of flowing fluid so as to move the heat therein with a greater effectiveness than is otherwise possible with smooth surfaced walls.

Various means" and methods have been devised to provide the inside and, the outside of tubes under construction with a form of heating surface that inherently increases the heat transfer surface. Methods have also been devised which effectively place an additional or extended surface upon an already constructed tube, however .such I methods are frequently damaging to the tubes inasmuch as considerable force must be applied thereto in the forming process and the tubes thus formed are consequently distorted. and the passageways therethrough thus deformed. v

It is therefore the principle'obje'ctive of this invention to provide a method of making a heat exchanger tube with a form of surface on its inner and outer walls that effectively increases the surface areas thereof and similarly increases its rate of heat transfer. A

It is a further specific objective of this invention to provide a method-of making an effective heat exchanger tube that is marked by ease, and accuracy of manufacture and which results in efficiency of use.

It is a still further objective of 'my invention to provide a method of impressing a predetermined form of extended surface on a flat material sheet before it 'isformed into a tubular configuration.

SUMMARY OF THEINYEblTION This invention is therefore directed to a method of forming a tubular heatexchangemember having extended surface on the sides thereof. .The method defined by the invention provides a tubular heat exchange member which is accurate and undistorted in form and is marked by economy in manufacture.

BRIEF DESCRIPTION OF THE DRAWING The invention will be best understood upon consideration of these objectives in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a material sheet formed in accordance'with this invention in preparation for bending into a tubular member; 7

FIG. 2 is a perspective view of a material sheet being formed into a tubular configuration;

FIG. 3 is a perspective view of a finished tubular member made according to this invention;

FIG. 4 is a diagrammatic representation of an embossed metallic sheet being formed in a die according to this invention; K

FIG. 5 is a diagrammatic representation of a sheet being formed into a tubular member without first being embossed and subjected to a bending die; and

The invention proposes to impress a form of extended surface on a substantially plane sheet of material before the sheet of material is placed in a bending die and bent longitudinally in a predetermined manner to produce a tubular member of desired configuration. By first placing the extended surface of desired form on a plane sheet of material a more precise control of the finished product is attained inasmuch as the finished tubular member need not be subjected to further bending forces sufficient to deform or disfigure the material thereof.

A plane sheet of material is accordingly formed to include a unique longitudinal embossing at its center and at its lateral sides at the same time that an extended surface is impressed on its surface. A sheet so formed is then subjected to a bending force in a bending die capable of concentrating the bending force along the center line of the longitudinal embossing. Free ends of the bent sheet are then held in abutment and bonded together to produce a tubelike member. Inasmuch as the heat exchange surface on the tube is formed at the longitudinal embossing is formed upon the sheet, no additional forming force is required to impress the extended surface thereon after the tube is completed.

In FIG. 1 of the drawing each tube consequently comprises a flat sheet of material 10 on which are formed as by rolling any of certain types of extended surface configurations shown by way of example as corrugations 12.'The corrugations may be produced on the flat sheet 10 by rolling or by pressing according to any acceptable process inasmuch as the method by which the corrugations, dimples or other form of extended surface are placed thereon immaterial to the invention itself.

The plane sheet 10 is at the same time formed to include a longitudinal-embossing l4 midway between its sides and also at its side edges where the rounded side of the tubular member is to be located. The sheet 10 is thus formed at its sides with radius r along the edges-l6 that lie substantially parallel to the embossing 14. The embossing 14 comprises essentially an evenly formed undulation'intermediate the side edges and on a single side of the principle plane of said sheet. The embossing so formed is then reversely bent at its crest whereby the top outer surface of the embossing will become the inner surface of one rounded side of the tubular member, and the curved edges 16 of the sheet 10 having the radius r will become the rounded inner edge of the remote side of the plane sided tubelike member. 7

The central embossing may have any predetermined lateral distance w designed toproduce a tubular member having a cross section or spacing between lateral sidesthereof suitable for the application for which the tubular heat exchange member is intended.

Inasmuch as the sheet 10 when embossed at I4 and 16 already is partially formed, only the crest of the undulation I4 need by arcuately reversed to form the sheet in the manner shown by FIG. 2.

To effect reversal of the longitudinal bend at the center or crest of the embossing 14, the embossed sheet I0 is placed in a bending die 15-17 with the die parallel to the crest of the embossing. As the members 15 and 17 of the die arrangement are brought together the force thereof depresses the erethane insert 22 and effects a shape to the sheet therebetweeen similar to the mating surfaces of the die 15-17.

FIG. 5 is an illustrative plane sheet being formed into a tubelike member without the benefit of first subjecting the sheet to an embossing action and then to a bending die, while FIG. 6 schematically shows the configuration imparted to a plane sheet as it has no previous embossing but a bending die is used to bend the sheet at its midpoint. Inasmuch as the sheet 10 has no central embossing 14, side embossing 16 or extended surface formed on the surface thereof, a tubular member formed therefrom would require substantial working with a probability of serious deformation before the desired shape is attained.

While we have illustrated and described a preferred embodiment of an invention, it is to be understood that this description may be modified within the purview of the appended claims.

We claim:

1. The method of making a tubular member for a heat exchanger or the like from a substantially plane sheet of material comprising the steps of forming said sheet to include an embossed portion which connects opposite ends thereof, reversely bending said sheet along the crest of the embossed portion whereby the top outer surface of the embossing will become the inner surface of the tubular member, and joining together side edges of said sheet to comprise an enclosed tubular member having a predetermined configuration.

2. The method of making a tubular member as defined in claim 1 wherein said embossed portion is formed evenly on said sheet from one to the other end thereof to produce a continuously even bend.

3. The method of making a tubular member as defined in claim 1 wherein a form of extended surface is placed upon said sheet of material before it is bent along the embossed portion thereof.

4. The method of making a tubular member as defined in claim 3 wherein the extended surface comprises a corrugated form impressed upon said sheet of material before bending it into a tubular form.

5. The method of making a tubular member as defined in claim 4 wherein the form of extended surface impressed upon said sheet of material lies laterally adjacent said embossed portion.

6. The method of making a tubular member as defined in claim 3 wherein the extended surface lies laterally adjacent, opposite sides of said embossed portion 7. The method of making a tubular member as defined in claim 1 wherein bending said sheet along the embossed portion thereof is effected in a bending die which concentrates a bending force along a line midway between sides of the embossing.

8. The method of making a tubular member as defined in claim 1 wherein the step of forming the sheet to include an embossed portion intermediate side edges thereof includes forming the edges of said sheet with aradius of curvature similar to that imparted to said embossed portion therebetween.

9. The method of making a tubular member as defined in claim 8 wherein said curved portion at the side edges of said sheet and the embossed portion therebetween are formed similarly and offset in the same direction from the principle plane of said sheet.

10. The method of making a tubular member from a substantially plane sheet of material comprising forming said sheet of material to include a line of embossing at the side edges and an embossing in the form of a U-shaped undulation midway therebetween that extends uniformly between ends of said sheet, forming extended surface on the face of said sheet intermediate lines of embossing, reversely bending said sheet along the central embossing whereby the top outer surface of the embossing will become the inner surface of the tubular member, and joining together edges of the sheet at the sides of the embossing to comprise an open ended tubular member having extended surface on the lateral sides thereof. 

1. The method of making a tubular member for a heat exchanger or the like from a substantially plane sheet of material comprising the steps of forming said sheet to include an embossed portion which connects opposite ends thereof, reversely bending said sheet along the crest of the embossed portion whereby the top outer surface of the embossing will become the inner surface of the tubular member, and joining together side edges of said sheet to comprise an enclosed tubular member having a predetermined configuration.
 2. The method of making a tubular member as defined in claim 1 wherein said embossed portion is formed evenly on said sheet from one to the other end thereof to produce a continuously even bend.
 3. The method of making a tubular member as defined in claim 1 wherein a form of extended surface is placed upon said sheet of material before it is bent along the embossed portion thereof.
 4. The method of making a tubular member as defined in claim 3 wherein the extended surface comprises a corrugated form impressed upon said sheet of material before bending it into a tubular form.
 5. The method of making a tubular member as defined in claim 4 wherein the form of extended surface impressed upon said sheet of material lies laterally adjacent said embossed portion.
 6. The method of making a tubular member as defined in claim 3 wherein the extended surface lies laterally adjacent, opposite sides of said embossed portion.
 7. The method of making a tubular member as defined in claim 1 wherein bending said sheet along the embossed portion thereof is effected in a bending die which concentrates a bending force along a line midway between sides of the embossing.
 8. The method of making a tubular member as defined in claim 1 wherein the step of forming the sheet to include an embossed portion intermediate side edges thereof includes forming the edges of said sheet with a radius of curvature similar to that imparted to said embossed portion therebetween.
 9. The method of making a tubular member as defined in claim 8 wherein said curved portion at the side edges of said sheet and the embossed portion therebetween are formed similarly and offset in the same direction from the principle plane of said sheet.
 10. The method of making a tubular member from a substantially plane sheet of material comprising forming said sheet of material to include a line of embossing at the side edges and an embossing in the form of a U-shaped undulation midway therebetween that extends uniformly between ends of said sheet, forming extended surface on the face of said sheet intermediate lines of embossing, reversely bending said sheet along the central embossing whereby the top outer surface of the embossing will become the inner surface of the tubular member, and joining together edges of the sheet at the sides of the embossing to comprise an open ended tubular member having extended surface on the lateral sides thereof. 